Make-up valve for hydraulic control circuit

ABSTRACT

A closed reservoir is connected to a pump for delivering pressurized hydraulic fluid to a directional control selector valve operatively connected to the ends of a double-acting hydraulic cylinder. A first check valve is positioned between the pump and the selector valve to pass pressurized hydraulic fluid thereby whereas a second check or make-up valve is telescopically mounted within the first check valve in exposed relationship to the hydraulic fluid contained in the reservoir. The make-up valve opens when the fluid pressure in the reservoir exceeds a predetermined level whereby such fluid is communicated therethrough and to the selector valve.

United States Patent [191 Dezelan Dec. 18, 1973 MAKE-UP VALVE FOR HYDRAULIC CONTROL CIRCUIT Inventor:

US. Cl. 91/6, 91/441, 91/446 Int. Cl'. F01h 25/02, F15b 1 1/08, FlSb 13/042 Field of Search 91/441, 6, 446;

60/DIG. 10, 477

References Cited UNITED STATES PATENTS 3.213.762, l0/l965 Dubuf. r. 9l/44l Stein et al.

Darling 91/44] Primary Examiner-Paul E. Maslousky Att0rneyPaul S. Lempio [5 7] ABSTRACT A closed reservoir is connected to a pump for delivering pressurized hydraulic fluid to a directional control selector valve operatively connected to the ends of a double-acting hydraulic cylinder. A first check valve is positioned between the pump and the selector valve to pass pressurized hydraulic fluid thereby whereas a second check or make-up valve is telescopically mounted within the first check valve in exposed relationship to the hydraulic fluid contained in the reservoir. The make-up valve opens when the fluid pressure in the reservoir exceeds a predetermined level whereby such fluid is communicated therethrough and to the selector valve.

8 Claims, 2 Drawing Figures MAKE-UP VALVE FOR HYDRAULIC CONTROL CIRCUIT BACKGROUND OF THE INVENTION Hydraulic control circuits for earthworking vehicles, such as tractors having hydraulically actuated work implements mounted thereon, oftentimes comprise a closed reservoir which may become ruptured when the fluid pressure therein exceeds a predetermined safe level. For example, such adverse condition may arise when a work implement is lowered by a hydraulic cylinder with the engine stopped. Hydraulic fluid exhausted.

to the reservoir from the cylinder becomes highly pressurized, particularly since a typical non-rotating engine driven pump is incapable of passing hydraulic fluid thereby. Applicants assignee has substantially overcome such problem by mounting a directional control selector valve within the reservoir along with a check valve positioned between the pump and selector valve and a separate, make-up valve, exposed interiorly of the tank, to relieve such unduly high fluid pressures.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWING Further objects of this invention will become apparent from the following description and accompanying drawing wherein: 1

FIG. 1 schematically illustrates an improved hydraulic control circuit having selector, check and make-up valves of this invention suitably integrated therein; and

FIG. 2 is an end view of the valves, taken inthe direction of arrows lI-ll in FIG. 1.

DETAILED DESCRIPTION FIG. 1 illustrates a hydraulic control circuit comprising a closed reservoir 10, shown in broken lines, adapted to be mounted on an earthworking vehicle such as a tractor. A hydraulic actuator 11, preferably comprising a double-acting hydraulic cylinder, is mounted on the tractor to perform a work function such as the selective raising or lowering of a ground engaging ripper (not shown). An engine driven pump means 12 communicates with the reservoir via a conduit 13 and with a directional control selector valve means via a conduit 14.

The selector valve means is mounted in the reservoir and is operatively connected to conduit 14 by first passage means 15, formed in a housing 16'thereof. Second passage means 17 and 18 are also formed in the housing to communicate the selector valve means with the head and rod ends of cylinder 11, respectively. The selector valve means further comprises a three-position valve spool 19 adapted to be manually positioned to eit-her the lower L, hold H or raise R position of cylinder operation.

The valve spool is normally and automatically maintained in its illustrated H position of operation by a conventional spring assembly 20, operatively associated with the right end thereof. Upon rightward movement of the valve spool to its L position, pressurized fluid from first passage means 15 will flow past a first check valve means 21, through a slot 22 and into a passage means 17 communicating with the head end of cylinder 11 to extend same. Simultaneously there with, the rod end of the cylinder is exhausted via a passage means 18, a second slot 23 and an exhaust passage 24 communicating with the reservoir.

When the valve spool is moved leftwardly'to its R position to retract the cylinder, the above sequence is reversed. In particular, pressurized fluid will communicate from first passage means 15, past check valve 21, through slot 23 and into passage means 18 to pressurize the rod end of cylinder 11. Simultaneously therewith, the head end of the cylinder will be exhausted via passage means 17, slot 22 and an annular chamber 25 which communicates with the reservoir. It should be noted that when the valve spool is maintained in its illustrated hold H position of operation, that annular passages 26 communicate pump 12 directly with the reservoir.

First check valve means 21 comprises a cup-shaped cylindrical member 27 normally urged rightwardly by a coil spring means 28 to have its closed end engage an annular seat 29 formed on the housing. A second check or make-up valve means 30 comprises a similar cupshaped cylindrical member 31 telescopically mounted within member, 27. Common spring means 28 also abuts member 31 to urge its closed end leftwardly against an annular seat 32 which is axially spaced from seat 29. Third passage means, preferably formed through the two back-to-back check valve means, comprises a plurality of apertures 33 formed at the reduced end of member 31, the cylindrical chambers formed within members 27 and 31 and apertures 34 formed at the reduced end of member 27.

An end cover plate 35 of the housing, preferably having seat 32 formed thereon, is secured in place by cap screws 36 (FIG. 2). centrally disposed opening 37 is formed through the plate to expose the closed end of member 31 to the fluid pressure level prevalent in the reservoir. When such level exceeds a predetermined amount, valve member 31 will move rightwardly to communicate fluid from the reservoir to the third passage means, formed through the two check valve means, and to the selector control valve means.

For example, it may be assumed that the engine (not shown) for driving pump 12 is, not. running and that se lector valve spool 19 is moved to its L position to extend cylinder 1 1 to lower a ripper (not shown) attached thereto. In many conventional systems, lacking a valve corresponding to makeup valve means 30, the pressure in the reservoir may become unduly high to buckle or possibly rupture same. However, when such pressure level is exceeded in the FIG. 1 circuit, make-up valve mally exist in the head end of cylinder 11 is substantially eliminated to permit the cylinder to function smoothly. It should be further noted that check valves 21 and 30 and plate 35 can be applied to conventional systems with only slight modification thereto.

What is claimed is: 1. A hydraulic control circuit comprising a closed reservoir for retaining hydraulic fluid therein, a hydraulic actuator, pump means communicating with said reservoir for pressurizing hydraulic fluid received therefrom, selector valve means mounted in said reservoir and operatively connected to said pump by first passage means and to said actuator by second passage means for selectively communicating said pressurized hydraulic fluid to said actuator, first check valve means in said first passage means for opening when said pressurized hydraulic fluid exceeds a first predetermined level to communicate said hydraulic fluid to said selector valve means, second check valve means exposed to said hydraulic fluid in said reservoir for opening when such hydraulic fluid exceeds a second predetermined level, and third passage means at least substantially defined by each of said first and second check valve means for communicating hydraulic fluid from said reservoir to said selector valve means upon opening of said second check valve means. 2. The invention of claim 1 wherein said hydraulic actuator comprises a double-acting hydraulic cylinder. 3. The invention of'claim 2 wherein said selector valve means has three operating positions, namely (a) a first position for communicating said first passage means with a head end of said cylinder and for simultaneously exhausting a rod end of said cylinder; (b) a second position for communicating said first passage means with a rod end of said cylinder and for simultaneously exhausting the head end of said cylinder; and (c) a third position for blocking communication of said first passage means with said second passage means.

4. The invention of claim 1 further comprising a cover plate detachably mounted on a housing containing each of said selector, first check and second check valve means and means forming an opening through said cover plate to expose said second check valve means to fluid pressure in said reservoir. 7

5. The invention of claim 1 wherein said first and second check valve means are mounted in back-to-back relationship with respect to each other in a housing, spring means for urging said first and second check valve means away from each other and means defining axially spaced annular seats therein, each of said first and second check valve means engaging a respective one of said seats to normally close said first and third passage means, respectively.

6. The invention of claim 5 wherein each of said first and second check valve means comprises a cylindrical cup-shaped member, said cup-shaped members telescopically mounted together.

7. The invention of claim 6 wherein said third passage means comprises at least one port and an internal chamber formed within each of said cup shaped members.

8. In an integrated control circuit comprising a closed reservoir, an actuator, a pump, a directional control selector valve mounted in said reservoir, check valve means for opening to communicate pressurized fluid from said pump to said selector valve and make-up valve means for opening to communicate fluid from said tank to said selector valve, the invention wherein said first and second check valve means are mounted in back-to-back relationship with respect to each other and define a continuous passage for communicating fluid from said reservoir to said selector valve upon opening of said second check valve means.

e UNITED STATES PATENT OFFICE. CERTIFICATE OF CORRECTION Patent No. 3,779, 33 1 Dated December 18, 197 4 Joseph E. Dezelan Inventor(s) It iscertified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column l; Claim 8: Line '8, aftef "ea'id" delete "first and second";-

after "means? insert --a nd said inake up valve means--; "Line 12, after "saidf'eqelete "seconQiehec lf" and insert --drake-511pin place thereof.

Signed ehd sealed thisi 3rd day of December I974.

(SEAL) Attestr Nancy M. emsoN JR. 0. MARSHALL 1mm Attesting Officer I Commissionerof Patents FORM PO-IOSO (\0-69) 3 r V T QscoMM-oc wan-Pu u.s GOVCRNHIIIIT umrmc orncz: an 0-30 3 

1. A hydraulic control circuit comprising a closed reservoir for retaining hydraulic fluid therein, a hydraulic actuator, pump means commuNicating with said reservoir for pressurizing hydraulic fluid received therefrom, selector valve means mounted in said reservoir and operatively connected to said pump by first passage means and to said actuator by second passage means for selectively communicating said pressurized hydraulic fluid to said actuator, first check valve means in said first passage means for opening when said pressurized hydraulic fluid exceeds a first predetermined level to communicate said hydraulic fluid to said selector valve means, second check valve means exposed to said hydraulic fluid in said reservoir for opening when such hydraulic fluid exceeds a second predetermined level, and third passage means at least substantially defined by each of said first and second check valve means for communicating hydraulic fluid from said reservoir to said selector valve means upon opening of said second check valve means.
 2. The invention of claim 1 wherein said hydraulic actuator comprises a double-acting hydraulic cylinder.
 3. The invention of claim 2 wherein said selector valve means has three operating positions, namely (a) a first position for communicating said first passage means with a head end of said cylinder and for simultaneously exhausting a rod end of said cylinder; (b) a second position for communicating said first passage means with a rod end of said cylinder and for simultaneously exhausting the head end of said cylinder; and (c) a third position for blocking communication of said first passage means with said second passage means.
 4. The invention of claim 1 further comprising a cover plate detachably mounted on a housing containing each of said selector, first check and second check valve means and means forming an opening through said cover plate to expose said second check valve means to fluid pressure in said reservoir.
 5. The invention of claim 1 wherein said first and second check valve means are mounted in back-to-back relationship with respect to each other in a housing, spring means for urging said first and second check valve means away from each other and means defining axially spaced annular seats therein, each of said first and second check valve means engaging a respective one of said seats to normally close said first and third passage means, respectively.
 6. The invention of claim 5 wherein each of said first and second check valve means comprises a cylindrical cup-shaped member, said cup-shaped members telescopically mounted together.
 7. The invention of claim 6 wherein said third passage means comprises at least one port and an internal chamber formed within each of said cup shaped members.
 8. In an integrated control circuit comprising a closed reservoir, an actuator, a pump, a directional control selector valve mounted in said reservoir, check valve means for opening to communicate pressurized fluid from said pump to said selector valve and make-up valve means for opening to communicate fluid from said tank to said selector valve, the invention wherein said first and second check valve means are mounted in back-to-back relationship with respect to each other and define a continuous passage for communicating fluid from said reservoir to said selector valve upon opening of said second check valve means. 